Drive circuit for pulsed inductive windings

ABSTRACT

A pulse forming drive circuit for a high speed counter actuated by a solenoid wherein a pulsing switch controls the energization of the solenoid. The drive circuit is connected in parallel with the solenoid and includes a capacitor and a resistor each connected across the solenoid and a rectifier connected in series with the capacitor and resistor to prevent the flow of current therethrough when the pulsing switch is closed but allows the flow of current therethrough when the magnetic switch is open to delay the normal voltage spike and then use the delayed voltage spike to promote the rapid decay of the magnetic field energy of the solenoid.

Unite States Patet Gamble [54] DRIVE CIRCUIT FOR PULSED ENDUCTIVE WINDINGS [72] Inventor: John G. Gamble, Simsbury, Conn. [73] Assignee: Veeder Industries Inc.., Hartford, Conn. [22] Filed: July 29, 1970 [21] Appl.No.: 59,190

[52] [1.8. CI ..235/92 C, 235/92 J, 235/92 R, 317/DIG. 6, 317/11 E, 307/104, 307/136 [51] Int. Cl. ..G06m 1/04 [58] Field ofSearch ..235/92 C, 92 J; 3 17/11 E, DIG. 6; 307/136, 104

[56] References Cited UNITED STATES PATENTS 3,322,937 5/1967 OBrien ..235/92 C 3,193,733 7/1965 Orsino.. ..3l7/DIG. 6 3,306,030 2/1967 Wiley ..235/92 C 51 June 6, 1972 OTHER PUBLICATIONS Arc, Surge, and Noise Suppression" by R. M. Rounyak, Electronics World, May 1967 pages 46- 48.

Primary ExaminerThomas A. Robinson Assistant Examiner.loseph M. Thesz, Jr. Attorney-Prutzman, Hayes, Kalb & Chilton [5 7] ABSTRACT nected in series with the capacitor and resistor to prevent the flow of current therethrough when the pulsing switch is closed but allows the flow of current therethrough when the magnetic switch is open to delay the normal voltage spike and then use the delayed voltage spike to promote the rapid decay of the magnetic field energy of the solenoid.

4 Claims, 1 Drawing Figure PATENTEDJUH 6 m2 3. 668 374 INVENTOR JOHN G. GAMBLE BY WWW ATTORNEYS DRIVE CIRCUIT FOR PULSED INDUCTIVE WINDINGS This invention relates to drive circuits for pulsed inductive windings and is particularly concerned with a circuit for a magnetically actuated high speed counter such as that disclosed in patent application Serial No. 672,786, filed Oct. 4, 1967 and assigned to the assignee of the present application.

A drive circuit for a high speed magnetically operated counter should provide for no loss of power during the buildup of flux in the solenoid operator of the counter upon the closing of the pulsing switch representing the movements to be counted, should prevent arcing at the contacts upon their opening irrespective of the speed of operation, should maintain the armature of the solenoid in its position a sufficient period to stabilize its power stroke, and then should maximize the rate of decay of the magnetic field so that the armature will drop out rapidly under minimum spring force.

A number of drive circuits have been developed for protecting the contacts controlling the flow of current to an inductive winding. However, each of these circuits either delays the build-up of the magnetic field in the winding upon closing the contacts, causes an undesired reduction in the flux duty cycle of the winding or delays the rate of decay of the magnetic field of the winding thereby decreasing the reliable high speed pulsed operation of the winding and increasing the power requirements thereof.

It is the primary object of this invention to provide drive circuit for a pulsed inductive winding which meets all the requirements for high speed operation.

Another object of this invention is to provide an improved voltage surge and arc suppressor circuit for a magnetically actuated solenoid which delays the voltage surge upon the opening of the pulsing contacts while providing for increased latch time for solenoid power stroke stability and maximum speed of reliable operation. Included in this object is the provision of electric circuit means for the maximum rate of decay of the magnetic field energy remaining in the solenoid at the end of the flux duty cycle thereof.

Other objects will be in part obvious and in part pointed out more in detail hereinafter.

The invention accordingly consists in the features of construction, combination of elements and arrangement of parts which will be exemplified in the construction hereafter set forth.

In the drawing:

The single FIGURE is a schematic wiring diagram illustrating the invention.

As shown in the drawing, an inductive winding which may be a solenoid having a spring-biased armature 12 engageable with a ratchet wheel 14 of a counter 16 for advancing the count indicated by the counter in discrete steps indicative of the number of movements being counted. A pulser, e.g., switch contacts 18, is provided for closing and opening the dc. electrical circuit for energizing the solenoid 10 in response to the movements to be counted which result in the closure of the switch 18 by a switch actuator 20.

In accordance with this invention, the drive circuit for the winding 10 is connected in parallel with the winding 10 and includes a unidirectional current device, e.g., rectifier 22, poled to prevent the flow of current therethrough when the switch 18 is closed to complete the circuit through winding 10. The drive circuit also includes a low impedance device, e.g., capacitor 24 connected in series with the rectifier 22, and a means for dissipating the magnetic field energy of the winding, e.g., resistor 26 connected across the terminals of capacitor 24.

In the operation of the illustrative counter, when the switch 18 is closed a unidirectional voltage is applied across the solenoid 10 to actuate the armature 12 against a return biasing means, e.g., a spring, to actuate the ratchet wheel 14 as disclosed in application Ser. No. 672,786 to change the total count indicated by the counter 16. When the switch 18 is closed, the rectifier 22 prevents any flow of current through the capacitor 24 and the resistor 26 so that there is no loss of power and. no time delay in the energization of the solenoid 10 to provide the most rapid rate of build-up of flux in the solenoid 10 for actuating the armature 12.

Immediately upon the opening of the contacts 18, the capacitor 24, which is then discharged, offers a transient short circuit through rectifier 22 for the magnetic field energy of the solenoid 10 so that the normal voltage spike which occurs as the contacts 18 begin to open is delayed and there is no arcing.

As the magnetic field in the solenoid 10 is dissipated through the capacitor 24, the charge in the capacitor 24 builds up to a level at which the voltage across the capacitor is equal to the voltage across the solenoid 10.

Since the magnetic field energy of the solenoid acts to maintain a constant flow of current therethrough, a delayed voltage spike will develop in an effort to maintain the flow of current. The remaining magnetic field energy is then dissipated by power losses in the resistor 26 and the solenoid 10. Due to the voltage spike which can be of the order of 10 times the prior voltage across the solenoid 10, the remaining magnetic field energy is dissipated at a rapid rate and a spring having a minimum spring force may be used to rapidly return the armature 12 to its at rest position.

By virtue of the time delay produced by the charging of the capacitor by the magnetic field energy of the solenoid, beginning when the switch 18 opens, the flux duty cycle, that is to say, the period during which the solenoid is energized, to hold the armature 12 in its actuated position is increased to include a significant period of time when the switch 18 is open. This increased latch time increases the power stroke stability of the armature 18 by providing additional time for frictional forces to overcome the vibrations resulting from the bounce" of the moving parts of the counter due to the high speed movement thereof. This is possible because the delayed voltage spike aids in dissipating the remaining magnetic field energy rapidly after the flux duty cycle to require less time for dissipating the magnetic field of the winding 10 so that it is ready for the next count.

From the foregoing it will be apparent that this invention provides a drive circuit for an inductive winding, having no arcing across the contacts upon the opening thereof and increased flux duty time for power stroke stability and to maximize the speed of reliable operation of an armature associated with the winding.

As will be apparent to persons skilled in the art, various modifications, adaptations and variations of the foregoing specific disclosure can be made without departing from the teachings of the present invention.

I claim:

1. A pulse forming drive circuit for a winding having a pulsing switch for controlling the energization of the winding, said drive circuit connected in parallel with said winding and comprising a capacitor to pass the current generated by the magnetic field energy of said winding when said pulsing switch is opened, means for effecting the delayed dissipation of the magnetic field energy of the winding, and means for blocking the flow of current through said drive circuit when said pulsing switch is closed.

2. A drive circuit as recited in claim 1 wherein said delayed dissipation means comprises a resistor connected in parallel with said capacitor.

3. A drive circuit as recited in claim 1 wherein said blocking means is a rectifier.

4. An electromagnetically powered high speed counter having a solenoid, a spring biased armature actuated by said solenoid, a pulsing switch actuated in accordance with the movements to be counted, and a pulse forming drive circuit for said solenoid connected in parallel therewith, said drive circuit comprising a rectifier to prevent the flow of current therethrough when the pulsing switch is closed, a capacitor in series with said rectifier and providing a low impedance path to pass the current generated by the magnetic field energy of said solenoid when said pulsing switch is opened and a resistance connected in parallel with said capacitor to rapidly dissipate the magnetic field energy of said solenoid to efiect the release of said armature after the capacitor is charged to a voltage equal to the voltage across said solenoid. 

1. A pulse forming drive circuit for a winding having a pulsing switch for controlling the energization of the winding, said drive circuit connected in parallel with said winding and comprising a capacitor to pass the current generated by the magnetic field energy of said winding when said pulsing switch is opened, means for effecting the delayed dissipation of the magnetic field energy of the winding, and means for blocking the flow of current through said drive circuit when said pulsing switch is closed.
 2. A drive circuit as recited in claim 1 wherein said delayed dissipation means comprises a resistor connected in parallel with said capacitor.
 3. A drive circuit as recited in claim 1 wherein said blocking means is a rectifier.
 4. An electromagnetically powered high speed counter having a solenoid, a spring biased armature actuated by said solenoid, a pulsing switch actuated in accordance with the movements to be counted, and a pulse forming drive circuit for said solenoid connected in parallel therewith, said drive circuit comprising a rectifier to prevent the flow of current therethrough when the pulsing switch is closed, a capacitor in series with said rectifier and providing a low impedance path to pass the current generated by the magnetic field energy of said solenoid when said pulsing switch is opened and a resistance connected in parallel with said capacitor to rapidly dissipate the magnetic field energy of said solenoid to effect the release of said armature after the capacitor is charged to a voltage equal to the voltage across said solenoid. 